<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <button id="btn">按钮</button>
    <script>
      btn.onclick = function () {
        // 发送ajax请求
        const xhr = new XMLHttpRequest()

        xhr.open('get', `http://localhost:5000/test`)

        xhr.send(null)

        // 接收响应
        xhr.onreadystatechange = function () {
          if (xhr.readyState === 4) {
            if (xhr.status === 200) {
              console.log(xhr.responseText)
            } else {
              console.log('失败了')
            }
          }
        }
      }
    </script>
  </body>
</html>
